Chemical mechanical polishing (CMP) is a process that is used to polish surfaces of semiconductor wafers. In particular, CMP employs both physical and chemical forces to polish wafer surfaces. First, a load force is applied to the back of a wafer while it rests on a polishing pad. Both the pad and the wafer are then counter-rotated while slurry containing both abrasives and reactive chemicals is passed underneath.
CMP is typically used to planarize a surface of a wafer for the purpose of creating an integrated circuit. CMP has emerged as the planarization method of choice because of its ability to planarize over longer lengths than traditional planarization techniques. As discussed, CMP is a combination of a chemical reaction and mechanical action. First, the slurry weakens the wafer surface and the slurry particles, in addition to particles located on the pad, complete material removal from the wafer surface.
It is desired to use aluminum nitride (AlN) as a substrate material for creating commercial semiconductor devices, however, there are problems in processing AlN surfaces to derive substrate surfaces suitable for epitaxial growth. For example, current CMP processes damage the AlN material making it unsuitable for epitaxial growth. It would be beneficial to have an improved method for polishing AlN wafers that produces a quality surface suitable for epitaxial growth.